Benzothiophene based semi-bis-chalcone as a photo-luminescent chemosensor with real-time hydrazine sensing and DFT studies†

Abstract

Hydrazine is a very toxic chemical that poses a major threat to human health and the environment. As a further expansion of our ongoing research, this report validates the enhanced real-time hydrazine sensing using benzothiophene-based semi-bis-chalcone (SBC). Hypothesized SBC molecules that can be easily attacked by nucleophilic groups were synthesised via classical Claisen–Schmidt condensation. Two derivatives of novel SBC scaffolds were synthesised by the reaction of simple acetone with benzothiophene carbaldehydes. This reaction involved the use of KOH and pyrrolidine as catalysts, and they demonstrated two different processes in comparative studies. KOH worked as a speedy catalyst, while pyrrolidine was demonstrated to be a more efficient catalyst. The structures of the synthesised compounds were established by various spectral techniques. The optical properties of the prepared SBCs were studied in different solvent systems and demonstrated that methanol was the more suitable solvent. Density functional theory (DFT) calculations of both compounds in methanol were performed using the Gaussian software. Time-dependent density functional theory (TDDFT) calculations were performed to study the dynamic behaviour of electrons in both molecules and materials by considering their density as a function of time. Both DFT and TDDFT calculations were observed to have a good correlation with the experimental results. The obtained absorption and photoluminescence results and their theoretical correlation suggested that the prepared SBCs can be optimized for applications in optoelectronics, sensing, and bioimaging. As an improvement to our earlier protocol, more efficient real-time hydrazine sensing SBCs probes were established with prolonged π-conjugation. An exhaustive protocol with a working pH range, analyte selectivity, and real sample test was developed. The studied SBCs showed a broad working pH range and excellent hydrazine sensing selectivity. With these two included in our large library of photoresponsive molecules, we aim to construct a model device for hydrazine sensing in real life applications.